Hey guys, my Jaguar was running great, started it up this week after a days (it was raining for several days) and the Failsafe Engine Mode showed up on the dash. Weirdly the engine and transmission still have full power no jerking super smooth nothing noticeable. I checked some areas for dampness in trunk or wiring harness but see nothing out of the unusual. I'm taking it to my mechanic, any ideas as to what may cause this, the car still runs great turns on every time etc

Thanks
Paul

 

Many random faults and DTCs are caused by a failing or weak battery. Have your battery tested.

 

Battery test little while ago and recharged, fairly new batter, it test out okay but will do so again.

Thanks!

 

About halfway down on this page, open the "S-Type Powertrain Introduction":

JagRepair.com - Jaguar Repair Information Resource

Scroll down to pages 25-28 for a description of the throttle control system. Specifically, see page 28 for more details of Fail Safe mode. Straight from the horse's mouth:

Failure Modes
There are four failure modes:
• Loss of redundancy eg a failure of one sensor output: this type of fault causes the AMBER warning light to illuminate and FAIL SAFE ENGINE MODE to be displayed on the message centre (the engine remains fully functional).
• Cruise inhibit
• Limp home mode in which a high idle speed is set, with no accelerator pedal response, to allow the vehicle to creep: the RED warning light and FAIL SAFE ENGINE MODE message
are activated: this mode is set by, eg the loss of two or more sensors.
• Engine shutdown due to serious throttle malfunction.


If you're only getting the message, amber light, and no other symptoms, it sounds like you're in the first failure mode, i.e. a loss of redundancy caused by the failure of one sensor output. The system has only two sensors. One is the output from the pedal, and the other is the position feedback on the throttle body.

IIRC, most OBD code readers won't show any faults for failsafe mode. OBD is primarily for reporting emissions-related faults, and this is only a control fault. Your shop may need a scanner that can retrieve Jaguar-specific non-OBD codes to know the exact fault. Many professional level scanners can do this, but most generic home-level scanners can't.

 

Some (all?) S-Types have two sensors on each of accel pedal & on TB (throttle body) and the car cross-checks they are consistent.